It is known that ketones or mixtures of ketones and aldehydes can be converted to resinous products in the presence of basic catalysts or acids. For instance, resins can be prepared from mixtures of cyclohexanone and methylcyclohexanone (Ullmann's Encyclopedia of Industrial Chemistry, Vol. 12, p. 551). Cyclohexanone and formaldehyde react to give hard resins which find use in the coatings industry.
Processes for preparing such products are described, for example, in U.S. Pat. No. 2,540,885, U.S. Pat. No. 2,540,886, DD 12433, DE 1300256, DE 2831613, DD 123481 and DE 1256898, all listed references are incorporated by reference.
According to DE 2831613, polycondensation products are obtained from aliphatic or cyclic ketones or mixtures of these ketones with aliphatic aldehydes in the presence of basic catalysts using from 0.005 to 10 mol %, based on the total amount of ketone and aldehyde, of a phase transfer catalyst. It is known to those skilled in the art that the process disclosed there can only provide resins having very high softening points and, as a result, high molecular weights. Since one use of the resins is in the coatings industry to reduce the solvent fraction, such high molecular weights are particularly disadvantageous. It is also known to those skilled in the art that cyclohexanone-formaldehyde resins lose their broad solubility properties at an excessively high molecular weight. Moreover, it is known to those skilled in the art that resins according to the processes described have low non-volatile fractions, which can have a negative influence on the thermal stability, and the yields of the process described are low.
It is also known that methyl ketones and cyclic ketones add to formaldehyde under preferably basic conditions to form the corresponding methylol compounds (stage 1). Depending on the pH and temperature, such methylol compounds dehydrate to form the corresponding vinyl ketones (stage 2). Under basic conditions, vinyl ketones in turn add to active hydrogens of the ketones by the mechanism of Michael addition, resulting in ketone-formaldehyde resins as the end product (stage 3).
In the processes used hitherto, formaldehyde is used in the form of 30 to 37% aqueous solutions. The catalyst consists of 50% aqueous sodium hydroxide solution or potassium hydroxide solution or a mixture of aqueous alkali and phase transfer catalyst.
The use of aqueous solutions and, for example, of sodium hydroxide solution greatly restricts the process in several respects:                (1) The ketones only have a limited solubility in water, so that, to achieve adequate reaction rates, large amounts of methanol or ethanol have to be used as solubilizers. These solvents reduce the space-time yield, lead to wastewater/waste air problems and are expensive to recover in a crude/purified form.        (2) The use of sodium hydroxide solution as a catalyst permits workup only by washing procedures which are particularly time-consuming. The necessary neutralization, for example, by means of acetic acid to give sodium acetate, additionally makes the wastewater costs more expensive.        